Dehydrator with means for directing emulsion through alpha high intensity field



H. F. FISHER 1,838,928

DEHYDRATOR WITH MEANS FOR DIRECTING EMULSION THROUGH HIGH INTENSITY FIELD Dec. 29, 1931.

Filed July 2, 192' asneets-sneet 1 wax/L A TTORJZEY.

F. FISHER Dec. 29, 1931.

DEHYDRATOR WITH MEANS FOR DIRECTING EMULS ION THROUGH HIGH INTENSITY FIELD 2 Sheets-Sheet 2 Filed July 2. 192' 01am: flaw) Patented Dec. 29, 1931 UNITED STATES PATENT. oFFlcE HABMON F. FISHER, E LONG BEACH, CALIFORNIA, ASSIGNOR TO PETROLEUM RECTIFY- ING COMPANY, OF CALIFORNIAQOF LOS ANGELES, GALIFORNIA. A CORPORATION OF CALIFORNIA DEHYDRATOR WITH MEANS FOR DIRECTING EMULSION THROUGH A HIGH INTENSITY FIEI] Application filed July 2, 1927. Serial No. 203,253.

This invention relates to dehydrators which are suitable for separating the phases of an emulsion. My invention may be used on many different emulsions such as edible oils,

or petroleumoils; and may also be used for treating other fluids or mixtures. In the following description I shall illustrate a dehydrator for petroleum oils, but do not intend to limit myself thereby.

The ordinary type of dehydrator consists of a tank in which a pair of electrodes are placed. These electrodes are separated so as to provide atreating'space and are connected in an electric circuit so that an electric field may be impressed upon the treating space. Emulsion to be treated is introduced into the tank and passes between the electrodes where it is subjected to the action ofthe electric field. The electric field acts upon the emulsion in such a manner as to coalesce the water'particles to a greater or less 'extent according to the design and efficiency of the dehydrator. a

I have found that there is a marked difference in the effectiveness of an electrical dc hydrator depending upon the character of the electric treating field and upon the exact part of the field in which the emulsion is treated. By the character of the electric treating field I have reference particularly to the distribution of the potential gradient across the gap between the electrodes of different potential.

By suitable design a dehydrator can be built to provide an electrode of such shape or form that the potential gradient in the treating zone between the two electrodes will not 'vary uniformly in direct ratio to the distance between the two, but will'be greatly concentrated on the surface of one of them, thus giving rise to an electrode of a higher or maximum field intensity. For example, in the case of a uniform distribution across a. gap of two inches between electrodes and acrosswhich a potential of 10,000 volts is impressed assume a point situated midway of the two electror s. The potential difference between this point and either of the two'ele'c= trodes will be practically one-half of the total impressed difference of potential or 5,000

volts. This is equivalent to an average graclient on either side of the midway 5,000 volts per inch. I 1

On the other hand, a point midway between the electrodes separated two inches apart and designed especially for a. non-uniform distribution of potential may be caused to have point of v a potential difference between itself and the electrode of lowest field intensity of but 2,000 volts and between itself and'the electrode of highestfield intensity of 8,000 volts. In this case, the same total difference of potential impressed across the two electrodes will be non-uniformlydistributed, and the average,

, will be treated but very little It will be seen then that if emulsion is to'be efficiently dehydrated in a minimum period of time its passage through the dehyrators treating space must be determined; therefore, if I introduce the emulsion before treatment into that portion of the field having the maximum field intensity or the highest potential gradient perinch, as already referred to above, it, in general, will pass through the field thoroughlytreated. Under these conditions fiheiluid surrounding or adjacent to the electrode of lowest field intensity, and forming a dielectric barrier around said electrode, is subjected to a relatively lower stress than is the emulsion in the maximum intensity field and will not readily rupture, therefore preventing short-circuiting currents between the electrodes and thus maintaining them at the highest possible difference of potential.

My experiments have shown that the most efficient treatment of emulsion is received b causing it to follow along or effectually paraf: l'el to the electrode of highest field intensity,

trode, this envelope traveling lengthwise over the surface of the electrode of highest and to form an envelope around this elecfield intensity for a distance to eifectcomplete treatment. I find that, in general, this distance is relatively short.

It is accordingly an important object of this invention to provide a dehydrator which is designed so as to have a field with a maximum intensity field portion and a minimum intensity field portion, and in which emulsion is maintained in the maximum intensity field portion for a sufficient length of time to effect the desired treatment.

T o accomplish this object of my invention I find it desirable to provide adjacent to the electrode of highest field intensity a member or nozzle which is designed to direct the emulsion along the electrode of highest field intensity. Means is also provided for supplying emulsion under pressure to the member or nozzle, this arrangement giving the emulsion proper direction and the desired velocity so that the kinetic energy imparted to it will cause it to travel in the desired manner and desired distances in the maximum intensity field portion of the electric field.

It is another object of the invention to provide an electric dehydrator of the general nature referred to in which the emuslion to be treated is supplied to the maximum intensity field portion with the desired velocity and direction so that the kinetic energy imparted thereto will cause the emulsion to travel in this portion of the field for asuifieient length of time to be completely treated.

Another object of the invention is to provide a dehydrator in which there will be no short-circuiting.

In order to maintain a dielectric barrier around the electrode of minimum field intensity, it is important to provide for a free circulation of dry oil (or other dielectric liquid) around this electrode. This free circulation is accommodated by providing an open circuit around this electrode and designlng it so that an injector effectby the emulsion introduced into the maximum portion of the electric field is obtained.

An object of my invention is to provide a dehydrator of this general nature having a free circulation of dielectric liquid around the electrode of lowest field intensity.

Another object of the invention is to provide a means for maintaining and renewing the supply of dielectric liquid which surrounds the electrode of lowest field intensity, in which the electrode of lowest field intensity is so'disposed with respect to the nozzle which directs the emulsion to be treated along the high intensity electrode, that entering emulsion produces a suction or jetting effect upon the fluid surrounding the electrode assembly such that it causes this fluid to continuously flow over the electrode of lowest field intensity.

It is still a further object of my invention to provide a novel method of treating a fluid,

such as an emulsion, by the use of an electric field.

Other objects and advantages of the invention will be made evident hereinafter.

Referring to the drawings in which my invention is illustrated:

Fig. 1 is a vertical cross section.

Fig. 2 is a horizontal cross section taken on the line 22 of Fig. 1.

Fig. 3 is a horizontal cross section taken on the line 33 of Fig. 1.

F ig. 4 is an enlarged fragmentary section of the nozzle of a preferred form.

Fig. 5 is a section taken on the line 5-5 of Fig. 4.

Fig. 6 is a fragmentary view illustrating a second form of nozzle of the invention.

Fig. 7 is a fragmentary view illustrating a third form of nozzle of the invention.

Fig. 8 is a diagram illustrating the distribution of the intensity in the treating space.

Referring to Figs. 1 to 4 inclusive, particularly Fig. l, the numeral 11 represents a shell having a conical tight top 12 and a conical tight bottom 13. Extending through the top 13 is an insulator 15. A lower end 16 of thisinsulator projects a considerable distance into the interior of the shell 11 for reasons which will be explained later. Extending through the insulator 15 is a rod 17 and connected to the lower end of the rod 17 is a plurality of arms 18. These arms 18 support a substantially cylindrical or sleeve shaped live electrode 19 which is also denominated a surrounding electrode or exciting shield. The electrode 19 is formed in the shape of a Venturi-tube and has a throat portion 19 of smallest diameter, this portion-having frusto-conical apron portions 19 and 19 extending therefrom. The exciting shield 19 has an open circuit entirely around it and has a throat 20 near the upper end of it to assist the circulation of a dielectric liquid aroundit as will be described later. Extending upward through the bottom 13 is an emulsion supply pipe 22 which has a pressure pump 23 for suplying the emulsion to the dehydrator with a desired pressure. Connected to the upper end of the emulsion supply pipe 22 is a central electrode 24. The electrode 24 has a passage 25 formed through it which is in communication with the passage of the emulsion supply pipe 22. As will be seen with reference to Figs. 1 and 3, the central electrode 24 is concentric with the surrounding electrode 19 so that it is surrounded by a treating space 25 which is of equal distance on any side of it.

As illustrated best in Figs. 4 and 5 the upper end of the central electrode 24 is provided with threads 27 so that a directing member or nozzle 28 may be attached, this nozzle 28 being located in the throat 20. The nozzle 28 has a threaded cavity 29 into which the threaded end 27 is screwed. Projecting downward from the upper part of the nozzle 28 is a concentric lip 30 which provides an annular space 31 within and around the central electrode 24. The central electrode 24 is provided with a plurality of openings 33 which connect the passage 24 with the exterior thereof. These openings 33 are inside the lip 30 so that they connect to the annular space 31.

Mounted in the upper end of the shell 11 is an annular spray pipe 36 which is of substantially the same diameter as the surrounding electrode 19. The spray pipe 30 rests in a plane above the lower end 16 of the insulator 15. This precludes short-circuiting between these two parts. Perforations 37 are provided in the lower part of the spray pipe 86, and a supply pipe 38 is connected to the spray pipe 36.

The nmneral 40 represents a transformer having a secondary winding 41. The secondary winding 41 is connected by a conductor 42 to the rod 17 and is connected by a conductor 43 to the shell 11 which is grounded as indicated at 44. In this manner the central and surrounding electrodes 24 and 19 are included in an electric circuit and in this manner an electric field is established in the treating space 25. This electric field because of the design of the electrodes has a maximum field intensity portion which surrounds the central electrode 24. \Vith referenceto Fig. 3 the maximum intensity field portion is that portion of the electric field which rests inside the dotted circle 46. The outer portion of the electric field is a minimum intensity field portion in which the potential gradient is much lower than in the maximum intensity field port-ion. This is because of the fact that the lines of force radiate from the central electrode to the surrounding electrode so that the intensity must necessarily be smaller as the distance from the central electrode is increased. Refe-rrin'g to Fig. 8 which is a diagram illustrating the field intensity. 4? represents an electrodeof maximum field intensity or the central electrode 24, and 48 represents the electrode of lowest field intensity or the surrounding electrode 19. The distance between the electrodes, that is, the size of the treating space is two inches. The diiference of potential of the two electrodes is 10.000 volts, this being indicated by a vertical distance. The curve 50 represents the field intensity". At a. point midway between the electrodes 47 and 48 I find that the difference of potential between this point and the electrode of highest field intensity is 8,000 volts, andthe difference in potential betweenthis point and the electrode of minimum field intensity is only 2,000 volts. To illustrate the distinction between this field and the ordinary field of uniform distribution I have drawn a dotted line 51 which represents the potential of a field of uniform distribution across. the

gap. At the midway point the difference of potential between this point and either-cf the electrodes is 5,000 volts. This diagram illustrates the difference between the two types of fields and clearly shows that there is a very high intensity of field around the central electrode 24.

In using the apparatus, just described, the interior of the shell 11 is first filled with a suitable liquid dielectric barrier. I prefer to use dry oil as a barrier. By dry oil I mean oil which has substantially no water content. This dry oil is supplied to the spray pipe 36 through thepipe 38 flowing through the openings 37 into the shell-11. \Vhen the shell 11 has been completely filled.'the electric field is established in the treating space 25, this electric field having a maxin'ium intensity field portion and a minimum intensity field portion as heretofore pointed out. The pump 23 is then set into operation and wet emulsion to be treated is delivered through the emulsion supply pipe 22 to the central electrode. This emulsion flows through the openings 33 into theannular space 31 inside the lip 30 of the nozzle 28. The nozzle 28 because of its shape discharges into the throat 20 of the Vent-uri-tube electrode and directs the emulsion in a downward direction as indicated by arrows 55 of Figs. 1 and 4. The nozzle gives the emulsion theproper direction, and the pressure applied to the emulsion by the pressure pump 23 gives it sufiicient velocity to hold it in its course for a desired length of time. The. untreated emulsion is confined to an annular space enveloping the central electrode 24 substantially as indicated by the dotted line 56 of Fig. 1. It will be seen that this emulsion is confined in the maximum intensity field portion of the electric field. As pointed out heretofore it; is inthis portion of the field that the most effective treatment will takeplace. The main course of the dielectric barrier is indicated by arrows 57. This circulation of the dielectric barrier is effected by the injector action of the incoming emulsion in the throat 20. The circulation of the dielectric barrier is entirely around the exciting shield where the field intensity is low, and it is at once apparent that this barrier is subjected to an auxiliary field formed between the'exciting shield and the tank, this auxiliary field tending to further agglomerate' any entrained water particles which might be carried upward therewith. n additionitv will be noted thatthe barrier fluid is subjected to an intense field just prior to the time it comes in'contact with the emulsion discharged 1 /from the nozzle 28, this fieldbeing set up between the nozzle and the surrounding electrode 19 and being quite intense because of the fact that the nozzle is of larger diameter than the body of the central electrode 24. By this circulation the barrier is prevented from being diluted wit-h emulsion and consequently its eflicienc is maintained. The dry oil provides a sel -healing barrier which prevents a short-circuiting such as might occur if the wet emulsion filled the entire treating space.

As I have pointed out before it is only necessary that the emulsion be confined to the maximum intensity field portion for a suflicicnt time to thoroughly treat it. The length of time that the emulsion will be maintained in its course along the central electrode 24 depends upon its velocity which, of course, is in proportion to the pressure or the thickness of the emulsion envelope around the electrode 24 which may be varied by varying the diameter of the annular space 31. If the emulsion is not being treated sufficiently the pressure thereon may be increased so that it will hold its course for a longer distance in the maximum intensity field portion, or the diameter of the annular space 25 may be varied. The treated emulsion and the dry oil are withdrawn from the lower end of the shell 11 through a take-off pipe 58.

From' the foregoing description I believe it will be apparent that my invention has one very import-ant object in view, that is, to provide a construction in which emulsion to be treated is given proper direction and velocity to maintain it'in maximum intensity field portion in proper quantity and for a sufficient length of time to permit it to be thoroughly treated. There are, of course, other objects in the invention such as preventing short-circuiting.

I do not wish to limit the invention to the construction illustrated in Figs. 1 to 5 inclusive because of the fact that different principle of the invention. Various modifications may be made; for example, the emulsion may be introduced into the maximum intensity field portion near the center thereof. This may be accomplished by using a nozzle as illustrated in Fig. 6. This nozzle represented by the numeral has a central threaded portion 61 into which pipes 62 are screwed, these pipes 62 forming the central electrode. Extending upward and downward from the central part of the nozzle are lips 64 which provide annular spaces 65. Formed in the pipes 62 within annular .spaces 65 are openings 66 through which emulsion may pass into the annular spaces. This construction is substantially two of the nozzles 28 illustrated'in Figs. 4 and 5 and directs the emulsion along the pipes 62- in the same manner as the nozzle 28directs the emulsion along the central electrode 24.

Such a construction as this may be desirable where a high capacity is desired: A

treater of this general character is shown and claimed in my copending application, filed September 16, 1926. In the forms described, the emulsion is treater.

passed through the electrode itself. This is not essential to the invention but is convenient as a matter of construction. In Fig. 7- 1 show a novel arrangement in which the emulsion may be supplied from a means separate from the electrode. In this figure the numeral 68 represents an electrode which may be solid. A nozzle 69 is supported at the upper end of the electrode, this nozzle being in the form of a cap which encloses the upper end of the electrode. An annular passage and a radial passage 70 and 71 are provided. Thenozzle 69 is supported by an emulsion supply pipe 73 which supplies emulsion to the radial passage 71. This emulsion flows through the radial passage 71 and then through the annular passage 7'0 along the electrode 68.

Still other forms may be provided; for example, an entirely different type of nozzle would be required if the central electrode were the live electrode in place of being the grounded electrode.

This invention embodies principles similar to the invention presented in my application dehydrator with high field intensity grounded electrode, Serial No. 135,804, filed September 16, 1926. This invention, however, will not be conflicted with that application in View of the novel circulating system and novel electrode structure as well as the fact that the emulsion is confined to the maximum intensity field portion by the use of directing means andby the use of pressure applied to the emulsion.

The treater has been described as a dehydrator because of the fact that it is presented in this application in connection with the dehydration of a fluid. The invention in its broadest conception is a combination of elements which provides an electrical Since the invention consists of an electrical treater capable of treating various fluids, I do not intend to limit myself to the limited use presented herein. In the claims the terms fluid barrier and fluid to be treated, as well as the term .fluid in itself. shall have a broad interpretation.

I claim as my invention:

1. In a dehydrator of the class described, the combination of: a pair of electrodes providing a treating space therebetween; means for setting up an electric field in said treating space, said electrodes being designed so that saidelectric field has a maximum field intensity portion and a minimum field intensity portion; and means for introducing a fluid to be treated into the maximum field intensity portion of said electric field, and in the form of a stream moving along one of said electrodes, one of said electrodes being so shapedv that a barrier of treated fluid is circulated through said minimum field intensity ortion when said fluid to be treated passes t rough said maximum field intensity portion, the treated fluid forming said bar- I rier being withdrawn from one end of said treating space and introduced into the other end thereof in a manner to circulate around one of said electrodes in a closed path and flowing through said electric field with a minimum of mixing with said-fluid to be treated.

2. In a dehydrator of the class described, the combination of: an outer electrode similar in shape to a Venturi-tube; an inner electrode disposed longitudinally in said outer electrode, said electrodes defining a treating space; means for establishing in said treating space an electric field having its greatest intensity adjacent said inner electrode; and means for supplying a fluid to be treated to said treating space; Y In a dehydrator of the class described, the combination .of: an outer electrode similar in shape to a Venturi-tube; an inner electrode disposed longitudinally in said outer electrode, said electrodes defining a treating space; means for establishing in said treating space an electric field having its greatest intensity adjacent said inner electrode; and means for injecting a. fluid to be treated into the throat of said outer electrode and along said inner electrode through the zone of greatestfield intensity. I

4. A combination as defined in claim 3 in which said electrodes are submerged in a,

' similar in shape to a Venturi-tube.

tral electrode and in a direction parallel to I 6. A dehydrator electrode adapted to en-' close a treating space, said electrode having a throat portion and frusto-conical portions extending therefrom.

7. In an electric treater, the combination of: a central electrode providing a smooth cylindrical surface; an outer electrode around said central electrode and cooperating therewith in defining a treating space in which is established an electric field; and nozzle ineans intowhich said central electrode extends to define an annular space for projecting a'fluid envelope of the fluid to be treated around and in contact with said centhe surface thereof. 1 a

8. In anelectric treater, the combination of: a central electrode in the form of a pipe, said electrode providing one or more Open ings formed through the walls thereof at a given section; a nozzle providing .a lip surrounding said central electrode at' said given sectionand'se arated from the surface there- 30f by an annu ar spacein direct communication with sand openings; and means forde- 10. A combination as defined in claim 9 in which said meansincludesa nozzle for injecting said fluid into said treating space in the form of a fluid envelope surrounding and in contact with said central electrode.

11. In an electric dehydrator, the combination of: a central electrode; a surrounding electrode; means for maintaining a difference in potential between said electrodes; and nozzle means for supplying an envelope of fluid around and in contact with the surface of the central electrode, said nozzle means being at the same potential as said central electrode and comprising a lip concentric with the external surface of said central electrode and cooperating with said external surface in defining an annular space through which said fluid passes.

- 12. In 11 electric treater, the combination of: a. surrounding electrode; a central electrode extending into said surrounding electrode and insulated therefrom; means for settingup an electric-field between said electrodes; a nozzle means associated with said central electrode and providing an annular discharge space directed parallel to the surface of said central electrode and in such position as to project an annular stream of 1 uid along, around, and in contact with the surface of said central electrode and flowing smoothly therealong; and means for supplying said fluid to said nozzle under high pressure to project said fluid from said nozzle means with suflicient velocity to prevent any material spreading of said stream away from the surface of said central electrode until electric treatment of said fluid in said stream is effected. v

13. In an electric treater, the combination of: a surrounding electrode open atits ends and submerged in abarrierliquid; a central electrode extending into said surrounding electrode and insulated therefrom, there beingan electric field therebetween; nozzle means for flowing a stream of fluid into the space immediately around said central electrode to form a fluid envelope flowing smoothly along and around and in contact with said central electrode, said nozzle means drawing a portion of-said barrier liquid into said surrounding electrode around said fluid envelope and circulating said barrier liquidin a closed path through and around said surrounding electrode; and means spaced from said surrounding electrode and insulated therefrom to define an auxiliary electric field through which said barrier liquid moving in said closed path passes before being again drawn into said electric field between said surrounding and central electrodes.

14. A method of treating an emulsion by the use of a central electrode and a surrounding electrode, which method includes the steps of: setting up an electric field in the treating space between said electrodes; and forming a high-velocity stream of emulsion moving around and in colitact with the surface of said central electrode in the form of a smooth-flowing envelope, .said envelope being formed by jetting said emulsion along said central electrode at such velocity that it remains in contact with said central electrode without substantially spreading therefrom for a distance in said electric field sufficient to effect a treatment thereof.

15. A method as defined in claim 14 in which a liquid is positioned adjacent that end of said treating space into which saidwemulsion is introduced, the jet action of the incoming-emulsion drawing a stream of said liquid into said treating space in confining relation with said stream of emulsion thereby tending to hold said stream of emulsion in contact with said central electrode as said emulsion flows therealong.

16. A method of treating an emulsion, which comprises: establishing an electric field of non-uniform intensity thereacross; injecting a high velocity stream of said emulsion into only that portion of said-field which is of higher intensity and in such manner that said stream flows smoothly through that portion of said field of higher intensity without substantially spreading into the lower intensity portion of said field; and utilizing the injector action of the incoming emulsion to draw into said lower intensity portion of said field a liquid of higher dielectric strength than said emulsion whereby said stream of emulsion and said liquid of higher dielectric strength fiow through said field side by side.

17. In an electric treater for agglomerating the dispersed water phase of an emulsion, the combination of: a surrounding electrode; a central electrode extending into said surrounding electrode and cooperating therewith in defining a vertically disposed treating space open at its ends and in which an electric field is established; a tank enclosing said electrodes and containing a barrier liq uid in which said surrounding electrode is submerged; and means for jetting a stream of emu sion downward into said treating space in a manner to draw a stream of said barrier liquid downward into said treating space along with said emulsion and circulate said barrier liquid upward around said surrounding electrode, said yvater phase of said emulsion agglomerating in said treating space and dropping to the bottom of said tank, a portion of the oil phase of said emulsion being recirculated through said treating space as the barrier liquid. 7

18. In an electric treater, the combination of: nozzle means providing an annular lip; a central electrode extending into said annular lip and cooperating therewith in providing an annular passage around the surface of said central electrode;'pipe means separate from said central electrode and communicating with said nozzle means to form an annular stream of fluid flowing along said central electrode; and electrode means surrounding said central electrode and insulated therefrom to define an electric field through which said stream of fluid passes.

19. In an electric treater the combination of: a tank containing a liquid, a surrounding electrode in the form of a sleeve open at its ends and positioned in said tank to be surrounded by said liquid; a central electrode providing a smooth cylindrical surface and extending axially into said surounding electrode; a nozzle means into which said central electrode extends and providing a lip cooperating with said cylindrical surface of said central electrode in defining an annular discharge passage; and means for delivering the emulsion to be treated to said nozzle means under pressure whereby a high velocity stream thereof flows through said annular discharge passage and along said cylindrical surface, the injector action of said stream drawing into-one end of said surrounding electrode a stream of said liquidin said tank in enveloping relation with said high velocity stream of emulsion and moving this stream of liquid from the other endof said surrounding electrode and through the space between said surrounding electrode and said tank to said first named end of said surrounding electrode to set up a closed circulation path around said surrounding electrode.

- 20. In an electric treater the combination of: a grounded tank containing a liquid'of higher dielectric strength than the emulsion to be treated; a sleeve-shaped electrode submerged'in said liquid; a small central electrode extending into said sleeve-shaped electrode and grounded to said-tank; means for setting up aimain field between said central electrode and said sleeve-shaped electrode and an auxiliary. field between said sleeveshaped electrode and said tank, said main electric field being highly concentrated immediately around said central electrode; and

contacting said central electrode, said nozzle means being directed parallel to the surface of said central electrode and jetting said emulsion into said sleeve-shaped electrode with sufiicient velocity to draw said liquid of higher dielectric strength into said main field around said fluid envelope of emulsion and set up a circulation of said liquid of higher dielectric strength through a closed path linking both said main and auxiliary day of June, 1927.

21. In an electric treater the combination of: a surrounding electrode open at its ends. and providing a passage communicating with a barrier fluid; a central electrode extending axially into said surounding electrode and insulated therefrom whereby an electric field set up therebetween is highly concentrated adjacent said central electrode; a nozzle means of larger external diameter than said central electrode and electrically connected thereto and extending inside said surrounding electrode whereby a field is set up between said nozzle and said surrounding elect-rode, said nozzle means dlrectlng an envelope of emulsion along the surface of said central electrode and drawing into. said surrounding electrode an envelope of said barrier fluid which moves through said field between said nozzle means andsaid surrounding electrode prior to being moved into the field between said central and said surrounding electrodes.

In testimony whereof, I have hereunto set my hand at Los Angeles, California, this 27th HARMON F. FISHER. 

